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i 5 UNITED STATES- PATENT tries, j

ERNST o'rro n ARcKR, or TUPIZA, BOLIVIA, AND CARL FBANOKE, on

GASSEL, GERMANY, ASSIGNORS OF MANITOU, COLORADO.

ONE-THIRD TO CHARLES ADAMS, OF

Proctss F ROASTING AN'D AMALGAMATING eon) AND SlLVER ORES.

S PECIFIC ATION forming part of Letters Patent No. 293,157, datedFebruary 5, 1884.

Application filed June .26, 1883. No specimens.) Patented in 'B liviaAugustill, 1850.

:0 all whom may concern:

Be it known that we, ERNST O. FRANCKE, residing at' Tupiza, in theRepublic of B0- livia, and CARL FRANGKE, a citizen of Germany, residingat C assel, have invented certain new and useful Improvements inProcesses of Roasting and Amalgamating Gold and Silver Ores; andwe dohereby declare the following to be a full, clear, and exact descriptionof the invention, such as will enable others skilled in the art to whichit appertains' to make and use the same.

.Thisinvention relates to certain improve ments in roasting andamalgamating refractory silver and gold bearing ores, which usuallycontain,fbesides the sulphide of silver, the sulphides, antimonides,tellurides, and selenides of iron, lead,'zinc., &c., to a greater orless extent, for the purpose of, separating the precious from the basemetals and salts, as

more fully hereinafter specified. p

In the processes of roasting and amalgamating ores as heretoforepracticed, it has been the main object to chloridize thesilver to the 25 greatest possible extent during the roasting,

in order to bring it into condition for the subsequent process ofamalgamation. Such treatment, however, has not been found profitablewhen applied to the refractory ores above 0 mentioned; and it is theobject of our improvement to provide a process by which a largepercentage of the silver may be extracted from such ores withconvenience and profit. In our improved process of roasting andamalgamat- 3 5 ing ores, we attach no importance whatever to thechloridization in the act of roasting, but aim mainly to producesulphates and chlorides of iron, copper, and possibly zin c, in theroasting process, to act as reagents in the-sub- 0 sequent treatment ofthe ores.

Our invention consists, first, in an improved process of treating oresby subjecting the same, in connection with common salt, to a temperature sufficient only to partially chloridize the 5 silver and producethe sulphates of iron and copper, and possibly zinc, and too low toaffect the arsenides, antimonides, tellurides, and selenides, as morefully hereinafter specified; second, in an improved process of treatingthe ores by subjecting the same, in the form of pulp, with common saltand quicksilver, under the influence of heat, in copper or copper-linedpans having copper agitators, as more fully hereinafter set forth. i

In carrying out our invention an ore containing, besides the sulphidesof silver, iron, and copper, the arsenides and antimonides may be taken,for example, such being, as is well known, one of the most refractoryores. The salted ore is roasted in an ordinary calcining-furnace at atemperature sufficient to convert the sulphides ofiron' and copper intothe sulphate, but not sufficiently elevated to affect the arsenides andantimonides, The ore is kept at a proper teinperatureuntil the 6 5desired reactions are effected, which maybe determined by itsappearance, at which time the process is interrupted. It has been foundby experience that about the proper time to stop the process isindicated when the ore has lost its metallic appearance and has assumedan earthy appearance, the ore giving" off at the same time the peculiarantimonial smell. At this point about one-third of the silver will befound to be chloridized, although the amount 7 will vary somewhat,according to the charac ter of the ore, the main object at this stagebeing to leave arsenides, antimonides, selen ides, and telluridesintact, and to convert the sulphides of the base metals, with theexception of sulphide of lead (if the ore should contain any) and thesulphide of silver, into sulphates. The roasting of the ore should bevery light, the point being to convert the sulphides, with the exceptionof the sulphides of lead and silver, into sulphates,and that thearsenides, antimonides, selenides, andtellurides be left undisturbed.This diners essentially from the roasting for other, amalgamatingprocesses, which all aim to a total chloridization of the silver, whichis only obtained by long and complete roasting. In our process we giveno importance whatever to the chloridizing of the silver in roasting,only aiming at the formation of the sulphates of 5 iron and copper, andpossibly zinc, in the roasting process. After theore is sufficientlyroasted, it has added to it additional common salt,

(in all about ten per cent. parts, and about forty per cent, of water,by weight,) after which the mass is placed in the amalgamatingpans. Thepans are constructed of metallic, copper, or wood lined with copper, andagitators or grinders are constructed of copper, all iron or other metalbeing carefully excluded, for the reason that such metals would bedetrimental to the subsequent reactions, as will hereinafter appear.silver contained a few pounds of quicksilver are added, after chargingthe pan with the ore pulp, and the charge is heated by steamheat,preferably by the direct application of live steam. The quicksilver isintroduced in the form of a shower, being pressed through canvas. Theagitators are rotated, forcing the pulp toward the periphery of the panand back, during which the following reactions take placeviz, thesulphate before mentioned, resulting from the decomposition of thesulphides, in connection with the common salt, are mutually decomposed,forming subchloride of copper and sulphate of soda. If the ore does notcontain sufficient-copper, a small quantity of blue vitriol may beadded. The subchloride of copper thus formed and the sulphide of silverin the ore will be mutually decomposed, forming chloride of silver andsulphide of copper, which is precipitated, and metallic copper, which,in a nascent state and while under the influence of the galvaniccurrents established by the contact of the quicksilver and copper in asolution of metallic salts, will decompose the chloride of silver,forming chloride of copper, which is again converted into subchloride ofcopper by contact with the copper of which the apparatus is constructed,the metallic silver being dissolved by the quicksilver, forming silveramalgam. Thus it will be perceived'the subehloride of copper is the mainreagent to induce the amalgamation of the silver, rendering an initialchloridization of the silver in the roasting operation unnecessary. Caremust be taken not to have too much quicksilver at any time, as it mayattack the copper and carry metallic copper into the amalgam, especiallywhen grinding. The quicksilver, as above stated, is introduced in smallquantities, varying from one and one-half to two pounds to each onepound of silver at the start, and when samples, taken from time to time,show that the amalgam is dry, and has somewhat the appearance of silverfilings, another similar quantity of quicksilver is added, in twoconsecutive charges, at an interval of from about one and' one-half totwo hours. As soon as the quicksilver commences to dissolve thecopperthe amalgam of the silver is at an end. If the roasting has beenconducted properly, nearly all of, the silver will have been extractedfrom the ore, but in any case the amalgamation is To each pound of 7complete when the quicksilver begins todissolve the copper, which can bedetermined by a practical metallurgist by sampling the amalgam from timeto time and noting its appearance and feel when rubbed betweenthefingers. The grinding-plates may now be raised and more mercury addedto the mass, so as to collect the amalgam; or the whole mass may betransferred to a wooden settler, more mercury added, and the amalgamcollected and treated as usual. \Vhen the ore contains iron, asitsometimes'does, the sulphate of iron, as well as sulphate of copper,will be formed during the roasting process, which will be converted intochloride of iron, and will act in conjunction with the subchloride ofcopper in the subsequent amalgamating process.

Having thus described our invention, what we claim, and desire to secureby Letters Patent, is

1. The process described of extracting precious metals from refractoryores, the same consisting in roasting the ores with salt at such lowtemperature as will transform the sulphides of iron, copper, &c., intothe sulphates and leave the arsenides, antimonides, selenides, andtellurides undisturbed, and subsequently amalgamating said roasted ore,substantially as herein. described and set forth.

2. The process herein described of treating refractory'ores,consistingin salting and roasting the same at a low temperature forconversion of certain sulphides into sulphates without disturbing othermetallic salts, as described, and afterward treating the same in a pulpwith common salt and quicksilver, under the influence of heat and in thepresence of metallic copper, whereby, through a series of reactions, thesilver is reduced to a metallic state and amalgamated, substantially asset i forth.

3. The process herein described of treating refractory ores, consistingof the following steps: first roasting the ores at a low temperature,then subjecting them, while in a state of pulp with water, to the actionof common salt and quicksilver, under the influence of heat and in thepresence of metallic-copper, and finally adding quicksilver atsuccessive intervals in small quantities, substantially as and for thepurpose set forth.

In testimony whereof I affix my signature in presence of two witnesses.

. ERNST OTTO FBANOKE. \Vitnesses:

F. AvELINo ARAMAYO, R. RODRIGUEZ FESTIGO. In testimony whereof I affixmy signature in presence of two witnesses.

CARL FRANOKE. W'itnesses:

ALVESTO S. HOGUE,

J EAN GRUND.

